Chocolate is very bitter. The darker and bitterer a Chocolate bar, the more Cacao it has (and the better it is).
For more than 3000 years Americans have been consuming Chocolate. Sugar has been part of the mixture for about 10% of that time. The Mayans and Aztecs of the Americas consumed Chocolate bitter and often added chilies. It was used by the common people as a spice, while the royalty drank it straight and bitter. In Latin America, Cacao is often used in it's original role as a bitter spice. Try a Molé burrito sometime. Yum! Cacao did not know sugar at all until the European love for sugar combined them.
The sweeter something is, the more sugar it has and the less Cacao it has. Chocolate is not sweet. Sugar is sweet. Candy is sugar. If it is sweet, it is not Chocolate, it is candy. Cadbury®, Hersheys®, Nestlé®, Milka® and Kinder® bars are not Chocolate, they are candy, as is all milk chocolate.
In milk-chocolate-candy, what you are tasting is NOT Chocolate. A Hersheys® Bar is about 11% Cacao! (And it is only that high because the United States Food & Drug Administration REQUIRES a minimum of 10% Cacao solids!) Cadbury®, Kinder® and Milka® are less then that! Snickers® is less than 2%. These bars all contain very tiny portions of Cacao and huge quantities of sugar and other additives. All milk chocolate contains more sugar than Cacao! This is not Chocolate; Sugar is the largest portion, the primary ingredient, and the selling point. (People call candy bars like Snickers® "chocolate" but they have a much higher percentage of both sugar and nuts than Cacao. They should be called "Nut Candy".)
Since the mid-1990s a number of the smaller chocolate manufacturers have introduced bars that are 60% - 90% Cacao. These are real Chocolate. They are the only Chocolate i buy. You will notice that some of the bars that list a high Cacao content which have weak or unpleasant flavor. Nestlé makes a 70% bar that is just awful. The addition of extra Cocoa Butter into the bar can weaken the flavor and there are many different levels and qualities of Chocolate. See the Varieties Page for a discussion of the primary cultivars.
Sugar, vegetable oils, artificial flavors, fillers and milk solids are all much cheaper than Cacao. The candy companies use any filler they can to cut down on the quantity of Chocolate they use, in fact, since flavorless Cocoa Butter is cheaper than Cacao Paste, they even raise the quantity of that, all to avoid Chocolate. Low Cacao solids means less Chocolate flavor, less money for the farmer and a higher profit margin for the manufacturer. Cocoa Butter has a very high resale value and is therefore often replaced by vegitible or milk fats. people think it is vanilla